Production of middle distillate



M15' 31, 1960 R. B. MASON ETAL 2,938,855

PRODUCTIGN OF MIDDLE DISTILLATE Filed Aug. 29, 1956 3 Sheets-Sheet 1William F. Arey, Jr. Inventors Charles N. Kimberlin, Jr.

By Qui-Q du--L( Attorney May 3l, 196() R. a. MASON ETAI- PRODUCTICN OFMIDDLE DISTILLATE 3 Sheets-Sheet 2 Filed Aug. 29, 3.956

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Chorles N. Kimberlin, Jr

By M Attorney May 31, 1960 R. B. MASON ETAL. 2,938,855

PRODUCTION OF MIDDLE DISTILLATE Filed Aug. 29, 1956 3 Sheets-Sheet. 3

ne, j "6 w'ATER AnnlrloN FIG-III MIXING AND HYDROLYZING SECTION `e RalphB. Mason William F. Arey, Jr. Inventors Charles N. Kimberlin, Jr.

BY Wd! Attorney PRODUCTION or Mronnn nrsrlLLATE Ralph Burgess Mason,Livingston, William Floyd Arey, Jr., and Charles Newton Kimberlin, Jr.,Baton Rouge, La., assignors to Esso Research and Engineering Cornpany, acorporation of Delaware Filed Aug. 29, 1956, Ser. No. 606,823

5 Claims. (Cl. 20S- 71) The present invention relates to distillate fuelmanufacture and it pertains more specically to the manufacture of highquality distillate fuels such as heating oils, diesel fuel, jet fuelsand the like from naphthas boiling in the gasoline boiling range.

The principal object of the present invention is to provide a processfor converting low octane and/ or unstable naphthas into materials ofhigher value and higher boiling range.

Hitherto, oil refineries have been generally operated to maximizenaphtha production for use as gasoline motor fuel. Some naphthas are ofsubstantially lower octane value than others, but could be blended withhigh anti-knock constituents to produce gasoline blends of acceptablequality. However, with the introduction of `high compression ratioautomobile engines, the octane requirements of gasoline have beensteadily increasing, thus severely narrowing the choice of constituentssuitable as gasoline blending agents. Thus, much virgin naphtha andnaphthas resulting from catalytic cracking of gas oil, hitherto used asgasoline blends for engines of moderate compression ratio, can no longerbe used for this purpose. Similarly, refinery processes such asiiuidized coking of residua, and visbreaking operations produce naphthasthat are unstable and sludge forming, and are of too high sulfur contentfor satisfactory use as fuels.

Concomitant with the increasing accummulation of these relatively lowvalue naphthas in the refineries, there has grown up in recent yearssubstantial demands for hydrocarbons boiling in the middle distillaterange of about 300 to 750 F. The rapid growth of heating oilinstallations both here and abroad, and the rapid dieselization oftransportation equipment has caused the supply of middle distillate tobe out of balance with that of motor gasolines. However, operating crudeoil and distillate refinery processes to maximize middle distillateswould seriously interfere with the production of high quality naphthas.An object of the present invention is to provide middle distillate fuelswithout interfering with maximum high quality and octane gasolineproduction.

Thus, heretofore middle distillate fuels have been produced asby-products in the manufacture of gasoline, and such fuels of relativelyhigh quality could be obtained directly from fractions of the virgincrude oil or from the cracking of virgin crudes. The phenomenal increasein demand for middle distillate fuels has presented a serious problem tothe oil refining industry.

Middle distillates, or distillate fuels, generally boil in the range ofabout 350 to 750 F., the so-called heater oils boiling in the range of350 to 550 F., while diesel fuels boil at about 400 to 650 F.

In accordance with the present invention, renery imbalance betweengasoline and heating oil demands and stocks are restored by catalyticconversion of low quality naphtha fractions into middle distillates. Ina sense nited States Patent o this is the reverse of the hitherto trendof petroleum refining where the gasoline fraction was the desiredproduct, and where low grade gasoline fractions were upgraded to highanti-knock material by such processes as reforming or isomerization. Thepresent invention involves principally conversion of the naphtha intomiddle distillate by catalytic condensation reaction involving formationand reaction of an oleinic intermediate, if a completely saturatednaphtha, such as casinghead or virgin naphtha is initially fed into theprocess. In brief compass, it has been found that excellent yields ofhigh quality low gravity middle distillates may be obtained by thecatalytic conversion, in the presence of a boron fluoride-watercatalyst, of low quality naphthas containing at least some unsaturation.In one embodiment of the present invention naphtha is thermally,catalytically, or steam cracked to a relatively low degree ofconversion, forming substantial quantities of olefins which are thenpassed to the catalytic conversion zone. In another embodiment, lowgrade catalytic or coker naphtha is fed directly into the catalyticconversion zone or is mixed with virgin or casinghead naphtha prior toconversion. Though the presence of oleiins is a necessary intermediate,there is a net disappearance of naphtha over and n above the olefins,and it is probable that under the reaction conditions, polymerization isaccompanied by substantial alkylation.

The catalyst employed in the present invention consists of a liquidcomprising EP3 and Water. In general, it is preferred to use acomposition in which the amount of water present varies from 2 to l moisper mol of B123.

it is readily prepared by bubbling BF3 gas into water while keeping themixture cool.

Several critical conditions must be maintained in accordance with thepresent invention to obtain good yields of middle distillate.Temperatures must be in the range such that middle distillates ratherthan lubricating oil boiling range material is formed. Secondary,exceptionally intimate contacting of the mutually insoluble catalyst andhydrocarbon phases must be achieved to maintain an economical process.Thirdly, it is essential to obtain the highest degree of recovery andreuse of the catalyst.

The objects of the invention and its advantages will be more readilyapparent from the more detailed description hereinafter when read inconjunction with the accompanying drawings showing preferred embodimentsthereof.

Figure I is a diagrammatic representation of a preferred systememploying a multi-stage oper-ation wherein the catalyst ow iscountercurrent to the feed so that the most active catalyst is employedin the nal stages to convert the more non-reactive oleiins.

Figure ll is a diagrammatic representation of a preferred systememploying a multi-stage operation with concurrent ow of feed andcatalyst but with increasing reaction condition severity in the stages.

Turning now to Figure I, a naphtha feed comprising low quality octaneconstituents, such as virgin naphtha, is passed via line 2 to crackingzone 4 where, under carefully controlled conditions of 50 to 400p.s.i.g. and temperatures in the range of 950 to 1l00 F. at feed ratesin the range of 0.2 to 6 v./v./hr. to insure relatively low conversionof about 10% to 30% but high olefin selectivity, the naphtha ispartially converted to an oletinic product of substantially similarboiling range but of higher olefinicity, of the order of 5% to 20%. Theeiuent from cracking zone 4 is now passed, after light gas separation,via lines 6 and 8 into rst stage naphtha conversion reactor 10. Ifdesired, low quality oleinic naphtha, such as coker naphtha, may also bepassed to reactor via lines 7 and 8. If olenic naphtha is the only feed,cracking Zone 4 may be by-passed completely. It is absolutely essentialthat an intimate mixing of feed and catalyst take place within reactor10. Though mechanical agitation may be employed, it is far preferable toachieve this by dispersion of the reactants in a jet to form anemulsion. This emulsion, with recycle, permits control of the Vaverageresidence time, which is about 0.25 to 4 hours. It is preferred toemploy hydrocarbon to catalyst ratios in the range of 4/l to 8/1,although higher ratios containing less B133 may be employed. Thecontacting is carried out at pressures in the range of atmospheric to 50p.s.i.g., preferably atmospheric, and at temperatures in the range of 50to 150 F., preferably 75 to 120 F. In accordance with this embodiment ofthe present invention, along with the fresh feed land recycle emulsionvfrom the first stage, there is injected into the lower portion vofreactor 10 catalyst from the first stage settler- 22 and catalyst fromthe second stage, as will be shown more Vclearly hereinafter. Both ofthese catalysts are at least partially spent. ln the naphthapolymerizationalkylation process, some of the oleiins are far morereactive than others. Thus, at conditions of maximum conversion thisleads to sludge formation and catalyst degradation so that the catalystis not performing at maximum ethciency. Partially spent catalyst,however,

has been found to have sufficient activity to condense Y the morereactive oleiins. Thus, in accordance with this embodiment, rapidcatalyst degradation is prevented by the most reactive oleiins in theVfresh feed to reactor 10 by employing the fresh or restored catalyst tocondense the less reactive oleiins in a second stage, and condensing themore reactive oleiins with the partially spent catalyst from the secondcondensation stage.

The emulisiied reaction product, comprising unconverted naphtha andoleiins, BFS-H2O catalyst, and higher boiling hydrocarbons produced inthe reactor, is withdrawn from reactor 10 via line 12 and a portion ofthe emulsion, from 50% to 90%, is recycled to the reactor via lines 14and 8. The balance of the emulsion is passed to first stage settlingzone 22. The lower catalyst layer may be withdrawn through line 18 andin part recycled, or it may be in part or completely drawn off -via line24 for regeneration in a manner known per se, as by passage to acatalyst concentration section, not forming a part of this invention.

The hydrocarbon layer, containing in solution some of the catalyst, iswithdrawn from an upper portion of settler 22 through line 26 and isinjected through line 28 into the lower portion of second stage reactork30. Fresh or restored EP3-H2O catalyst is passed into zone 30 throughline 36, and, as inthe case of rst stage reactor 10, a portion of theemulsion withdrawn from the upper portion of reactor 30, is recycled tocontrol contact time. Reaction conditions in reactor 30 are generallythe same order of magnitude as in the first stage in terms of contacttime and rates.

In zone 30 the fresh or restored catalyst contacts the i less reactiveolens, and conversion of the olefinic material is substantiallycomplete.

The emulsiiied efliuent from the second stage withdrawn through line 32is in part recycled through line 34 to reactor 30, and the balancepassed to settling zone 40. The lower aqueous catalyst phase isWithdrawn through line 42 and in part recycled to reactor 30; the majorportion, however, is passed via lines 16 and 8 to first stage reactor l@wherein it contacts fresh feed as set forth above.

The upper, hydrocarbon layer containing some Vdissolved catalyst is nowpassed to fractionation section 50. Though the hydrocarbon layer may beWaterwashed to recover dissolved catalyst, this would require aconcentration step and reduced pressures which impose additionaloperation problems. In the preferred embodiment shown here, thehydrocarbon product is passed to distillation zone 50 where the desiredmiddle distillate fraction boiling in the range of 350 .to 750 F. issegregated and withdrawn through line 56. During the distillation, B133in solution, the dissolved BFS-H2O complexes, and some BFS-hydrocarboncomplexes Vare withdrawn in the lower boiling fractions. These fractionsare preferably recycled via lines 52 and 58 to reactor 30. Make up watermay be added to prepare the desired Elsa-H2O ratio catalyst.

Y The EP3-free naphtha is withdrawn as a side stream :through line 53and is advantageously recycled at least in part through line 54 to theolefin producing section of the system, here cracking unit 4. Similarly,heavy bottorns boiling above the middle distillate range may be passedvia line 60 to cracking unit 4.

Turning now to Figure II, there is described an embodiment of stagedreaction with concurrent dow. As previously pointed out, underconditions normally empioyed, catalyst is deactivated by polymerbuild-up with the more reactive olens. This'loss in activity and yieldfrequently renders the operation unprotable. These difficulties areavoided in the present embodiment by conducting the condensation instages of increasing severity as the operation proceeds. For thispurpose, four methods vmay be employed.

Save for the concurrent ow of catalyst and feed, the ow of streams inFigure li is substantially the same as in Figure I. For this reason, andin the interest of simplicity, only those portions of Figure II arenumbered that function differently from Figure I.

Turning now to Figure II, first stage reactor 70 receives fresh olefinfeed through line 72 and fresh recycle and reconstituted BF3-H2Ocatalyst through line 74. To second stage vreactor S0 there is fedpartially reacted hydrocarbon stream through line 86, and partiallyspent catalyst through lines S4 and 82. One method of achievingincreased severity in reactor over reactor 70 is to maintain thevtemperature in the latter at 30 to 50 F. while that in the former is at250? 'to 300 F. Concomitantly with, or instead of this temperaturedifferential, there is maintained in first stage 70 a more diluteBFS-H2O solution. Thus in reactor 70 there may be maintained a BF3concentration of 40% to 65%, based on BF3+H2O, while in reactor 80, aconcentration of 66% to 79% obtains. The latter is the saturation valueat atmospheric pressure.

Instead of, or along with increasing the temperature, the pressure maybe progressively increased. The initial stage 70 thus may be maintainedat atmospheric pressure while stage 80 may be at 500 to 600 psig., orhigher.

Unreacted olens separated from the final reaction product in thedistillation zone are preferably recycled to the Zone of increasedseverity.

The process of the present invention is further illustrated by thefollowing specific examples.

Example 1 l An example of the excellent performance of the boronfluoride-water catalyst has been shown experimentally. To 44.8 grams ofwater, boron uoride was added to the near saturation point at atemperature of about 50-75 F. To 206.5 grams of this solution 777.4grams of a naphtha from commercial catalytic cracking operations wasadded slowly'and with vigorousstirring at a temperature of about 50 F.and atmospheric pressure. Following the completeV naphtha additionagitation was continued for 4 hours at ambient temperature approximately80" F.) The total product Vwas transferred to a separatory funnel andthe lower layer was drawn oi. The upper layer was water-washed and wassubmitted for analysis. The following analytical data demonstrate theeectiveness of the operation. in the lproduction of` middle distillate(350-650 F. hydrocarbons).

assente This yield of 46% of middle distillate is near the ultimate forthis feed.

Example 2 Catalyst HzSOs BFa-Hzo HaPO4 Conc. of active component,

Wt. Percent 96 80 80 79 79 B5 Total v./v 44 54 108 43 159 65 Temp., F120 115 115 120 120 S0 Pressure (l) (l) (l) (l) (l) (l) Vol. Percent 350F.+Prod- 13 S 6 20 18 0 l Atmospheric.

These data show the marked superiority of the BFS-H2O catalyst. Notshown by the data were the diiculties experienced in sludge formationand acid re- -covery with H2SO4.

Example 3 In another experiment a catalytic naphtha of higher yolefincontent than used in the preceding experiments (Bromine No. 150 vs. 90)was treated as in Example 1. The yield of 350 F. plus product was 60%. Aseparate portion of this total product was distilled to 300 F. cut pointand under these conditions a 65 vol. percent yield of product useful asheating oil, etc. resulted.

Example 4 In another experiment a visbreaker naphtha of lower olefincontent (Bromine No. 61 vs. 90 and 150) was treated as in Example l. Theyield of 350 F. plus product was 22%. lt is observed that conditionsemployed during commercial visbreaking are similar to those for thecracking step in the previous disclosures.

Example 5 A highly selective production of middle distillate with theboron fluoride-water catalyst is shown by the Engler distillation dataon the total product from each of the feeds employed in the previousexamples. In each case the end point is 650 F. and less. The data are:

Feed Catalytic Visbrealrer Naphtha Naphtha Bromlne No 90 150 61 IBP, F113 123 138 138 141 164 150 201 160 262 170 358 172 410 182 454 200 507234 80% 560 384 632 510 95% 640 594 Example 6 In another set ofexperiments the advantages of staged operation are demonstrated. Theoperation as described in Example 1 was repeated with fresh feed butwith the same catalyst with a marked decline in catalyst activity. Thecomposited product from the second and third cycles, which wasincompletely converted, was contacted with fresh catalyst with the sameyield as obtained initially and with less catalyst degradation. The dataare:

Experiment 1 2 (Feed) Batch Operation B D Feed Catalytic Naphtha Comp.Prod.

from B and C 60/40 Blend.

Vol. Ratio, Feed/Cat., 9

An important feature of the present invention involves a novel means ofcatalyst recovery. In the` preparation of middle distillate by reactionof oletinic naphthas with boron uoride-water catalyst considerablepolymer is formed which remains with the catalyst. This decreases theactivity of the catalyst and necessitates catalyst replacement. For suchprocesses to' be economical a catalyst regeneration technique isrequired.

A11 excellent method of catalyst recovery consists in (1) separation anddrawing oli the lower or catalyst layer containing the deactivatingpolymer, (2) hydrolysis of the catalyst, (3) separation of the polymer,and (4) distillation of the water layer to recover the boron iiuoride.The feasibility of the process is demonstrated in an experiment in which4258 grams of a catalytic naphtha was contacted with 1187 grams of aboron fluoride-water preparation containing about 79% kboron liuoridc.From this operation 3456 grams of hydrocarbon and 1895 grams of aseparated lower layer were recovered. Of this lower layer 564 grams wereadded to 1265 grams of water and the charge was heated in an autoclavewith agitation for 4 hours at 400 F. The discharged product wasseparated into layers and the oil product was washed with Water toremove all traces of residual boron fluoride from the hydrolysis. Thehydrocarbon layer was analyzed and was found to contain 87.5% carbon and12.5% hydrogen. A separate analysis showed the complete absence offluoride which demonstrates the complete removal of boron uoridecatalyst and also demonstrates the hydrocarbon purity of the polymer.

Furthermore, by this technique the yield of high boiling hydrocarbons isincreased. Thus the 300 F. plus product from the original condensationand distillation was 56.2 weight percent of the original feed. Uponrecovery of the polymer this yield is increased to 72.7 percent.

The catalyst recovery process is shown in Figure Ill. Spent catalystwithdrawn through line 24 (Figure I) for regeneration is passed intohydrolyzing-mixing zone 104l where, after hydrolysis and settling (10S),the hydrolizer water is passed to an atmospheric distillation section114. The polymer settling out is scrubbed in water scrubber 122 andrecovered. ln 114 the aqueous BF3 is distilled at atmospheric pressure,gaseous BF3 and water going overhead and withdrawn through lines 146 and14S and 152.. The Water is limited to an amount less than that requiredto yield BFa-HZO. The two streams are combined to yield a catalystcontaining about 79% BFS. The water is returned via lines 134 and 120 tothe hydrolysis section.

Alternatively, the hydrolizer water may be distilled under reducedpressure in section 132, taking water overhead and leaving EP3-21120 asabottoms product.

The boron fluoride recovery from the hydrolyzer water may be done byeither of two 'distillation procedures or by a combination of both. inmethod A the aqueous boron lluori'de is distilled' at atmosphericpressure taking.

gaseous BF?, and' water overhead. The latter is limited to a `quantitysomewhat less than that requiredto yield BF3H2O. The two overheadstreams are combined, to yeild the catalyst containing about 79% boronuoride. The water is returned to the hydrolysis section.

Method B consists in distilling the bydrolyzer water under reducedpressure wherein water is taken overhead leaving as bottoms boronfluoride with two Waters of hydration. This can be fortitied with freshBPB, or can be concentrated as in method A. In cases where atmosphericpressure concentration is employed the bottoms are usually returned tothe reduced pressure distillation section to minimize boron liuoridelosses. The use of reduced pressure prior to the iinal concentrationaiords a recycle stream to the hydrolyzer of less boron tiuoridecontent.

The two concentrators may be used in combination with the hydrolyzersolution split with part going to each concentrator or the two may beused intermittently.

IThe process as described anords a more economical production of middledistillate from olelinic materials because a greater yield ofhighboiling polymer ofY high purity is achieved and because the catalystisl recovered for conY tinuous use.

What is claimed is:

1. An improved processr for converting paranic low octane naphthas intomiddle distillates boiling inthe range of from about 350". to 750 F.,which comprises passing said naphthas to a cracking Zone, maintaining yatemperature of from about 950 to 1100 F., pressure of from about 50 to400 p.s.i.g. and space velocity of from about 0.2 to 6 v./v./hr. in saidcracking zone, converting said naphthas in said `Zone to an ellluentcontaining about to 20% oletins, passing said eliiuent to a tworeactorolefin conversion system, maintaining pressures of from about 15 to 50psig., temperatures of from about 50 to 150 F. and a hydrocarbon tocatalyst ratio in the range of from about-4:1 to 8:1 in each of saidrecators, jetting said effluent into the rst reactor to form an emulsionwith partially spent BF3H2O catalyst from the second reactor,withdrawing the emulsion from said tirst reactor, separating a portionoisaid emulsion into an aqueous spent catalystfraction'and'a'hydrocarbon fraction, jetting said hydrocarbon fractioninto the second reactor to form a second yemulsion with fresh BF3H2Ocatalyst having a mol ratio of water to BF3 in the range of about 1:1 to2:1, withdrawing saidl second emulsion from the second reactor,separating a portion or" said second emulsion into a partially spentcatalyst fraction and a second hydrocarbon fraction, passing saidpartially spent catalyst fraction to the rst reactor, passing saidsecond hydrocarbon fraction to a fractionation zone and recovering amiddle distillate fraction from said fractionation zone.

2. The process of claim l wherein said spent catalyst fraction isregenerated in a process comprising passing said spent catalyst tractionto a hydrolysis zone, separating perature of from about 950 to` 1l00 F.,pressure of' from about 50 to 400 p.s.i.g. and space velocity of fromabout 0.2 to 6 v./v./hr. in said zone, converting said naphthas in saidzone tov an euent containing; about 5 to 20% olelins, jetting effluentYfrom` said zoneconcurfv rently withV fresh BFS'HgO catalystv havingk amol ratio of water to B133 in the range of about 1:1 to 2:-1 to form anemulsion in the first reactor of a two-reactor olen conversion system,maintaining a temperature of` from about 30 to 50 F. and low pressure insaid rst reactor, with-v drawing the emulsion from said firstreactonseparating a portion of said emulsion into an aqueous partiallyspent catalyst fraction and a hydrocarbon fraction, jetting a portion ofsaid aqueous partially spent catalyst fraction and said hydrocarbonfraction in the secand reactor totorm a second emulsion, maintaining atemperature of about 250 to 300 F. in said second reactor and recoveringfrom said second reactor good yields of middle distillate.

5. An improved process for converting parafinic low octane naphthas intomiddle distillates boiling in the range from about 350 to 750 F., whichcomprises passing said naphthas to a cracking zone, maintaining Iatemperature of from about 950L7 to 1l00 'F., pressure of from about 50to 400 p.s.i.g. andjspace velocityofV from about 0.2 to 6 v./v./hr. insaid zone, converting said naphthas in said zone to an eiiuentcontaining about 5 to 20% oleiins, jetting etlluent from said zone witha BFS-H2O catalyst containing about 40 to 65% EP3 to forman emulsion inthe first reactor of a two-reactor olefin conversion System, maintaininga temperature of frornraborut 30 to 50 F. and low pressure in saidfirstn reactor, withdrawing theV emulsion from said first reactor,separating a portion of said emulsion into an aqueous partially spentcatalyst vfraction and a hydrocarbon fraction, jetting a portion of saidhydrocarbon fraction with a BF3lH2O catalyst containing about 66 to 79%BF3 in the second reactor to form a second emulsion, maintaining atemperature of about'250 to 300 F. in said second reactor and recoveringfrom said second reactor good yields of middle distillate.

References Cited in the le of this .patent UNlTED STATES PATENTS ...aNew x

1. AN IMPROVED PROCESS FOR CONVERTING PARAFFINIC LOW OCTANE NAPHTHASINTO MIDDLE DISTILLATES BOILING IN THE RANGE OF FROM ABOUT 350* TO750*F., WHICH COMPRISES PASSING SAID NAPHTHAS TO A CRACKING ZONE,MAINTAINING A TEMPERATURE OF FROM ABOUT 950* TO 1100*F., PRESSURE OFFROM ABOUT 50 TO 400 P.S.I.G. AND SPACE VELOCITY OF FROM ABOUT 0.2 TO 6V./V./HR. IN SAID CRACKING ZONE,CONVERTING SAID NAPHTHAS IN SAID ZONE TOAN EFFLUENT CONTAINING ABOUT 5 TO 20% OLEFINS, PASSING SAID EFFLUENT TOA TWO-REACTOR OLEFINS CONVERSION SYSTEM, MAINTAINING PRESSURES OF FROMABOUT 15 TO 50 P.S.I.G., TEMPERATURES OF FROM ABOUT 50* TO 150*F. AND AHYDROCARBON TO CATALYST RATIO IN THE RANGE OF FROM ABOUT 4:1 TO 8:1 INEACH OF SAID REACTORS, JETTING SAID EFFLUENT INTO THE FIRST REACTOR TOFORM AN EMULSION WITH PARTIALLY SPENT BF3.H2O CATALYST FROM THE SECONDREACTOR, WITHDRAWING THE EMULSION FROM SAID FRIST REACTOR SEPARATING APORTION OF SAID EMULSION INTO AN AQUEOUS